Two huge, mysterious bubbles bubble out of the heart of the Milky Way, and now it seems that the bubbles could have doubles.
Scientists have known for a decade that two charged particle bubbles, or plasma, flank the plane of the Milky Way. These structures, known as Fermi bubbles by the telescope that recognized them, are visible in high-energy light called gamma rays (SN: 11/9/10). But now the eROSITA X-ray telescope has discovered larger bubbles that can be seen in X-rays. The X-ray bubbles extend about 45,000 light years above and below the center of the galaxy, researchers report online December 9th nature.
Previously, researchers had seen an X-ray arc over the galactic plane (SN: 07/08/20). However, no such feature was discernible below the level of the galaxy. This lack of symmetry led some scientists to rule out the possibility of x-ray bubbles. With the new results “this argument has now fallen,” says study co-author Andrea Merloni, astronomer at the Max Planck Institute for Extraterrestrial Physics in Garching. The eROSITA data shows a weak and previously unknown bubble below the galactic plane and a matching bubble above. The gamma-ray bubbles are nested within the X-ray bubbles, suggesting the two features are related, says Merloni.
Studying the bubbles could help uncover violent events that may have occurred in the galaxy’s past. The supermassive black hole in the middle of the Milky Way is currently pretty calm as far as black holes are concerned. But a previous feeding frenzy could have spat out its remains and formed the structures. Or the bubbles could have been the result of a time when many stars formed and exploded in the heart of the galaxy. Further examination of the x-ray and gamma-ray bubbles could help uncover the cause.